The object of this proposal will be to study the interactive toxicity of representative metals present in chemical waste dumps using rabbit renal cortical slices. Although the toxicity of chemical mixtures has received attention in a number of tissues, little effort has been expended towards the interactive toxicity of environmentally relevant chemicals in the kidney. Since metals retain their elemental identity, even during degradative processes, and their principal site for excretion is the kidney, the kidney lends itself as a pivotal site for interaction. Precision-cut renal cortical slices have proven to be a reliable in vitro renal system that allows us to examine the numerous potential interactions, readily apply a variety of analyses, and produce site-specific lesions which mimic in vivo. The Specific Aims are: 1) Determine the effect of two metal toxicants that affect the same site of the renal nephron. We are asking if two metals that affect the same area of the nephron are present, will they produce a synergistic, additive, or antagonistic effect? 2) Examine the effect of two metal toxicants that affect different but adjacent sites in the renal nephron. We now ask if two metals are present and they affect different but adjacent sites will the resulting toxicity be synergistic, additive, or antagonistic? 3) Determine if altered transport or uptake processes caused by one metal toxicant affect the uptake and toxicity of the second toxicant. The importance that uptake and transport plays in organic nephrotoxicants is well documented. Less is known about a metallic nephrotoxicants uptake and transport. We ask what is the importance of the specific ligands and transporters on the expression of toxicity of a specific metal toxicant and what affect a second metallic toxicant has on these processes? 4) Determine if metals do become localized in a specific target renal cells and if a second toxicant affects this uptake. A number of studies have highlighted the importance of threshold levels of metals in the kidney to produce their toxic effects. In conjunction with the Analytical Core and other projects, we will measure the uptake of the metallic toxicants, how another metal toxicant affects this uptake, and the overall homeostasis of metals in renal cells. By understanding the mechanism of these interactions, we hope to predict future interactions between metals which are present in chemical waste dumps and provide additional information for risk analysis.